Heat pipe

ABSTRACT

A heat pipe includes a casing and a three-dimensional cross-linkage wick structure received in the casing. The three-dimensional cross-linkage wick structure has a plurality of pores therein for providing a capillary action and includes a bottom layer being attached to the casing and a plurality of protrusions extending from the bottom layer and spaced from each other. A groove is defined between two adjacent protrusions. The bottom layer has a connecting portion under the groove. The connection portion is formed between and connects with the two adjacent protrusions. The connection portions have a smaller pore size than the protrusions.

BACKGROUND

1. Technical Field

The present invention relates generally to an apparatus for transfer or dissipation of heat from heat-generating components, and more particularly to a heat pipe applicable in electronic products such as personal computers for removing heat from electronic components installed therein.

2. Description of Related Art

Currently, heat pipes are widely used for removing heat from heat-generating components such as central processing units (CPUs) of computers. A heat pipe is usually a vacuum casing containing therein a working medium, which is employed to carry, under phase transitions between liquid state and vapor state, thermal energy from one section of the heat pipe (typically referring to as the “evaporator section”) to another section thereof (typically referring to as the “condenser section”). Preferably, a wick structure is provided inside the heat pipe for drawing the working medium back to the evaporator section after it is condensed at the condenser section. The wick structure currently available for the heat pipe includes fine grooves integrally formed at the inner wall of the casing, screen mesh or fiber inserted into the casing and held against the inner wall thereof, or sintered powders combined to the inner wall of the casing by sintering process.

In order to draw the condensate back from the condenser section to the evaporator section timely, the wick structure provided in the heat pipe is expected to provide a high capillary force and contain more working medium in the wick structure.

Therefore, it is desirable to provide a heat pipe with an improved heat transfer capability, whose wick structure provides a high capillary force and contains more working medium therein.

BRIEF DESCRIPTION OF THE DRAWINGS

Many aspects of the present embodiments can be better understood with reference to the following drawings. The components in the drawings are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of the present embodiments. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views.

FIG. 1 is a partially cross-sectional view of a heat pipe in accordance with a first embodiment of the present invention.

FIG. 2 is a microscopic view of a portion of a wick structure of the heat pipe of FIG. 1.

FIG. 3 shows a cross-sectional view of a heat pipe in accordance with a second embodiment of the present invention.

DETAILED DESCRIPTION

Referring to FIGS. 1 and 2, a flat heat pipe 10 includes a casing 11 and a three-dimensional cross-linkage wick structure 13 received in the casing 11, wherein the wick structure 13 has a plurality of pores therein and is saturated with a working medium.

The casing 11 is made of a highly thermally conductive material such as copper or aluminum and has an evaporator section at one end thereof and a condenser section at an opposite end thereof. The casing 11 includes a bottom plate 112 at a bottom side thereof and an upper plate 111 at a top side thereof opposite to the bottom plate 112.

The wick structure 13 is made of a highly thermally conductive metal material such as copper or aluminum. The plurality of pores in the wick structure 13 provides a capillary action for drawing the working medium condensed at the condenser section back to the evaporator section.

The wick structure 13 includes a bottom layer 131 and a plurality of protrusions 132 extending upwardly from the bottom layer 131. The bottom layer 131 is flat and attached to the bottom plate 112. The protrusions 132 are extended over an entire length of the heat pipe 10, from the evaporator section to the condenser section of the casing 11. A top of the protrusion 132 is attached to the upper plate 111, thereby supporting the top plate 11 to improve the robustness and flatness of the heat pipe 10. The protrusion 132 has a trapezium-shaped transverse cross section. In other alternative embodiments, the protrusion 132 can have a triangle-shaped or a rectangle-shaped transverse cross section. The protrusions 132 are spaced from each other, whereby a groove 133 is defined between two adjacent protrusions 132. The groove 133 is used as a vapor channel. The groove 133 extends longitudinally from the evaporator section to the condenser section of the casing 11. The bottom layer 131 has a connection portion 135 corresponding to and located just under the groove 133, wherein the connection portion 135 of the bottom layer 131 is formed between and connects with the two adjacent protrusions 132.

The protrusion 132 has a greater pore size than the connection portion 135 of the bottom layer 131, whereby the protrusion 132 has a lower flow resistance for the working medium and can contain more working medium condensed at the condenser section in the pores of the protrusion 132. The connection portion 135 of the bottom layer 131 has a smaller pore size than the protrusion 132, whereby the connection portion 135 has a larger capillary action than the protrusion 132. Thus, the condensed working medium at the condenser section of the casing 11 can flow more rapidly from the upper plate 111 toward the bottom plate 112 via the protrusion 132 under the capillary action of the connection portion 135. Then the condensed working medium flows along the bottom layer 131 from the condenser section to the evaporator section of the casing 11 for another heat transfer cycle.

FIG. 2 shows a microscopic view of a portion of the wick structure 13, in which the wick structure 13 has a large porosity and three-dimensional interlocking, whereby the wick structure 13 can have a better performance in the absorption and delivery of the condensed working medium than the conventional wick structure: mesh, sintered powder or tiny grooves.

The wick structure 13 is formed by first preparing a sponge with a predetermined porosity and pore size. Then the sponge is activated so that it can be electroplated with a metallic layer thereon. Thereafter, the electroplated sponge is put in a tank for subject to electrocasting whereby a copper (or aluminum) wicking structure is formed on the metallic layer, thereby to obtain a semifinished product. The semifinished is then heated at a high temperature to remove the sponge therefrom and sinter the copper wicking structure. Finally, the sintered copper wicking structure is pressed to form the grooves 133 in the sintered copper wicking structure to thereby obtain the wick structure 13, wherein the protrusions 132 have larger pores therein and the connection portions 135 have smaller pores therein.

FIG. 3 shows a round heat pipe 20 according to a second embodiment of the present invention. The casing 21 of the heat pipe 20 has a ring-like transverse cross section. The wick structure 23 is received in the casing 21 and defines a vapor channel 24 therein. The bottom layer 231 of the wick structure 23 is attached to an inner peripheral surface of the casing 21. The plurality of protrusions 232 extends radially and inwardly from the bottom layer 231 towards a center of the round heat pipe 20, in which a vapor channel 24 which communicates with a groove between two adjacent protrusions 232 is extended. The wick structure 23 is formed by the same method for forming the wick structure 13, except that they have a flat shape and a ring-like shape, respectively.

It is believed that the present embodiments and their advantages will be understood from the foregoing description, and it will be apparent that various changes may be made thereto without departing from the spirit and scope of the invention or sacrificing all of its material advantages, the examples hereinbefore described merely being preferred or exemplary embodiments of the invention. 

1 A heat pipe comprising: a casing; a three-dimensional cross-linkage wick structure received in the casing and having a plurality of pores therein for providing a capillary action, the three-dimensional cross-linkage wick structure comprising: a bottom layer being attached to the casing; and a plurality of protrusions extending from the bottom layer and spacing from each other, a groove being defined between two adjacent protrusions, the bottom layer having a connection portion just under the groove, the connection portion being formed between and connecting with the two adjacent protrusions, the connection portion having a smaller pore size than the protrusions.
 2. The heat pipe as claimed in claim 1, wherein the casing is flat and has an upper plate and a bottom plate being located under the upper plate, the bottom layer of the three-dimensional cross-linkage wick structure being flat and attached to the bottom plate, a top of each of the protrusions abutting on the upper plate.
 3. The heat pipe as claimed in claim 2, wherein the groove defined between the two adjacent protrusions is provided as a vapor channel.
 4. The heat pipe as claimed in claim 1, wherein the casing is round, the bottom layer being attached to an inner peripheral surface of the casing, the protrusions extending radially and inwardly from the bottom layer toward a center of heat pipe.
 5. The heat pipe as claimed in claim 1, wherein a shape of each of the protrusions is selected from a group consisting of trapezium, triangle, and rectangle.
 6. A heat pipe comprising: a casing; a three-dimensional cross-linkage wick structure received in the casing and having a plurality of pores therein for providing a capillary action, the three-dimensional cross-linkage wick structure comprising: a bottom layer being attached to the casing; a plurality of protrusions extending from the bottom layer and spacing from each other, a groove being defined between two adjacent protrusions, the bottom layer having a connection portion just under the groove, the connection portion being formed between and connecting with the two adjacent protrusions; and a working medium saturated in the pores of the wick structure; wherein the connection portions have a smaller pore size than the protrusions, the connection portions have a larger capillary force for the working medium in comparison with the protrusions, and the protrusions have a lower flow resistance for the working medium in comparison with the connection portions.
 7. The heat pipe as claimed in claim 6, wherein the casing is flat and has an upper plate at a top side thereof and a bottom plate at a bottom side thereof, the bottom layer of the three-dimensional cross-linkage wick structure being flat and attached to the bottom plate, a top of each of the protrusions abutting on the upper plate.
 8. The heat pipe as claimed in claim 7, wherein the groove defined between the two adjacent protrusions is provided as a vapor channel.
 9. The heat pipe as claimed in claim 6, wherein the casing is round, the bottom layer being attached to an inner peripheral surface of the casing, the protrusions extending radially and inwardly from the bottom layer toward a center of the heat pipe.
 10. The heat pipe as claimed in claim 6, wherein a shape of each of the protrusions is selected from a group consisting of trapezium, triangle, and rectangle. 